The present invention relates to the field of driveshafts and more particularly to driveshafts particularly useful in gas turbine engines.
Traditional fan shaft materials used in gas turbine engines are high strength steel and nickel-based superalloy which includes a spline and a thread in the forward end to hold a fan disk. It is desirable to employ a titanium metal matrix composite (MMC) fan shaft material due to its low density, high strength and high specific stiffness. However, this material cannot be threaded, turned or drilled due to fiber breakage and subsequent loss of load carrying capability or delamination. Joining of a superalloy end attachment to the MMC fanshaft becomes a major issue, particularly at temperatures above 800 degrees F, as brazing, diffusion bonding or inertia welding creates an unacceptably brittle intermetallic layer between the titanium composite and the superalloy shaft portion.